Personally, though, I think it's most likely that they came up with it the same way they did "Hyrule" or "Koholint", or how any author comes up with names for any story he/she writes, which seems to be mostly just random words that sounded cool at the time. That could just be me being naive, but it's just what I personally think.
Actually in any writing, names can mean a lot and most writers actually put a lot of thought into names, especially for significant things like main characters or fictional locations, but that's getting a bit off topic.
Termina, as many have already said, ties into the idea of an "end",derived from latin "terminus"-"to end", symbolically referring to the apocalyptic nature of the game's plot. I personally feel that there is another symbolic meaning to the name. Kaepora Gaebora implied that Termina was a land "destined to fade" or something along those lines. If that is the case, then the name Termina may have been given as a sort of prophesy, and that leads to all sorts of potential for odd theories I won't go into. At the same time, the fact that Termina was actually saved may indicate that the name was chosen for irony, a land named for its fate of dying actually survives in the end. In literature, it is said that irony trumps everything, so maybe the game creators felt like adding in some irony. *shrugs*
